U.S. patent number 5,164,170 [Application Number 07/715,270] was granted by the patent office on 1992-11-17 for synthesis of zeolite beta.
This patent grant is currently assigned to Mobil Oil Corporation. Invention is credited to Mae K. Rubin.
United States Patent |
5,164,170 |
Rubin |
November 17, 1992 |
Synthesis of zeolite Beta
Abstract
A large crystal zeolite Beta having a broad range of
silica-to-alumina ratios, i.e. 20-.fwdarw.1000, is synthesized with
triethanolamine in the synthesis mixture along with organic
directing agents such as tertraethylammonium hydroxide,
tetraethylammonium bromide and tetraethylammonium fluoride. The
highly silicious zeolite Beta is produced from a silica source
comprising precipitated silica and high purity, high silica starter
seeds.
Inventors: |
Rubin; Mae K. (Bala Cynwyd,
PA) |
Assignee: |
Mobil Oil Corporation (Fairfax,
VA)
|
Family
ID: |
24873335 |
Appl.
No.: |
07/715,270 |
Filed: |
June 14, 1991 |
Current U.S.
Class: |
423/709 |
Current CPC
Class: |
B01J
29/7007 (20130101); B01J 29/80 (20130101); C01B
39/48 (20130101); B01J 2229/36 (20130101); B01J
2229/37 (20130101); B01J 2229/38 (20130101) |
Current International
Class: |
B01J
29/00 (20060101); B01J 29/70 (20060101); B01J
29/80 (20060101); C01B 39/00 (20060101); C01B
39/48 (20060101); C01B 033/34 () |
Field of
Search: |
;423/328,329,330,277
;502/61,69,77,79 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Kuhl, G. H., "Crystallization of Zeolites in the Presence of a
Complexing Agent" Molecular Sieve Zeolites I vol. 101 ACS 1971 pp.
63-75. .
Charnell, J. F., Crystal Growth vol. 8, pp. 291-294 (1971). .
Camblor et al., Zeolites, vol. 11, pp. 202-210 (Mar., 1991). .
Morris et al., Zeolites vol. 11, pp. 178-183 (Feb., 1991)..
|
Primary Examiner: Breneman; R. Bruce
Attorney, Agent or Firm: McKillop; Alexander J. Speciale;
Charles J. Sinnott; Jessica M.
Claims
I claim:
1. A method of synthesizing a crystalline synthetic zeolite
comprising a large crystal zeolite Beta which ranges in size from
0.1 to 3.0 microns having a silica to alumina ratio of at least 20
to about 200 which is substantially free of amorphous materials and
having the structure of zeolite Beta prepared by:
(a) preparing a reaction mixture which contains one or more sources
of alkali metal cations, organic cation which is a
tetraethylammonium cation, triethanolamine, an oxide of silicon,
water and an oxide of aluminum and having reaction mixture in terms
of mole ratios within the following ranges:
where R is the organic cation, M is the alkali metal cation and X
is the triethanolamine;
(b) maintaining the reaction mixture under conditions sufficient to
crystallize the zeolite Beta wherein said large crystal zeolite
beta is substantially free of amorphous materials and has a
silica-to-alumina ratio ranging from about 20 to about 200; and
(c) recovering the crystalline zeolite Beta from step (b), the
recovered zeolite containing at least one organic cation and the
triethanoloamine.
2. The method of claim 1 in which the source of oxide of silicon of
the reaction mixture is selected from the group consisting of
colloidal silica, precipitated silica and silica precursor.
3. The method of claim 2 in which the source of oxide of silicon is
the precipitated silica or silica precursor and the reaction
mixture further comprises crystalline zeolite
4. The method of claim 1 in which the organic cation represented by
R and the triethanoloamine represented by X of the zeolite Beta
recovered in step (b) are converted into the hydrogen form at least
in part by calcining and exhange.
5. The method of claim 1 in which maintaining the reaction mixture
under conditions sufficient to crystallize the zeolite includes
temperatures ranging from 70.degree. C. to 175.degree. C.
6. The method of claim 3 in which the zeolite Beta seeds are
prepared by the synthesis as described in claim 1.
7. The method of claim 1 in which the organic cation source is
selected from the group consisting of tetraethylammonium hydroxide,
tetraethylammonium halide and a combination thereof.
8. The method of claim 7 in which the tetraethylammmonium halide
source is selected from the group consisting of tetraethylammonium
bromide, tetraethylammonium chloride, and tetraethylammonium
fluoride.
9. A process for the production of large crystal zeolite Beta
having a crystal size ranging from 0.1 to 3.0 microns and a
silica-to-alumina mole ratio of about 200 to about 1000 which is
substantially free of amorphous materials comprising the steps
of:
(a) preparing a reaction mixture which contains one or more sources
of alkali metal cations, organic cation which is a
tetraethylammonium cation, triethanolamine, water, a source of
aluminum, and a silica source which is an oxide of silicon and
having a reaction mixture in terms of mole ratios within the
following ranges:
where R is the organic cation, M is the alkali metal cation and X
is the triethanolamine, the reaction mixture also containing a
plurality of zeolite beta seeds;
(b) maintaining the reaction mixture under conditions sufficient to
crystallize the zeolite to produce a large crystal zeolite beta
having a crystal size ranging from 0.1 to 3.0 microns which is
substantially free of amorphous materials and which is
substantially free of contaminants; and
(c) recovering the crystalline zeolite beta.
10. The process of claim 9 in which the organic cation represented
by R and the triethanolamine represented by X of the zeolite Beta
recovered in step (b) are converted at least in part into the
hydrogen form by calcining and exchange.
11. The process of claim 9 in which maintaining the reaction
mixture under conditions sufficient to crystallize the zeolite
includes temperatures ranging from 70.degree. C. to 175.degree.
C.
12. The process of claim 9 in which the organic cation source is
selected from the group consisting of tetraethylammonium hydroxide,
tetraethylammonium halide and a combination thereof.
13. The process of claim 12 in which the tetraethylammonium halide
source is selected from the group consisting of tetraethylammonium
bromide, tetraethylammonium chloride and tetraethylammonium
fluoride.
14. The process of claim 9 in which the silica source has a solids
content of greater than about 78 wt.%.
15. The process of claim 9 which includes the step of agitating the
reaction mixture.
16. A process for the production of zeolite Beta having a
silica-to-alumina mole ratio of at least about 465 which is
substantially free of amorphous materials comprising the steps
of:
(a) preparing a reaction mixture which contains one or more sources
of alkali metal cations, organic cation which is a
tetraethylammonium cation, triethanolamine, water, and a silica
source and having a reaction mixture in terms of mole ratios within
the following ranges:
where R is the organic cation, M is the alkali metal cation and X
is the triethanolamine, the reaction mixture also containing a
plurality of zeolite beta seeds which are highly silicious and high
purity;
(b) agitating the reaction mixture under conditions of temperature,
ranging from about 70.degree. C. to about 140.degree. C. and time
ranging from about 16 hours to 10 days, sufficient to crystallize
the zeolite to produce zeolite beta which is substantially free of
amorphous materials wherein said triethanolamine facilitates
fluidization of the reaction mixture to produce the zeolite beta
which is substantially free of contaminants; and
(c) recovering the crystalline zeolite beta.
17. The process of claim 16 in which the organic cation represented
by R and the triethanolamine represented by X of the zeolite Beta
recovered in step (b) are converted at least in part into the
hydrogen form by calcining and exchange.
18. The process of claim 16 in which the organic cation source is
selected from the group consisting of tetraethylammonium hydroxide,
tetraethylammonium halide and a combination thereof.
19. The process of claim 18 in which the tetraethylammonium halide
source is selected from the group consisting of tetraethylammonium
bromide, tetraethylammonium chloride and tetraethylammonium
fluoride.
20. The process of claim 16 in which the silica source has a solids
content ranging from 30 wt.% to 90 wt.%.
21. The process of claim 20 in which the silica source has a solids
content of at least 87 wt.%.
22. The process of claim 16 in which the zeolite beta seeds have a
silica-to-alumina mole ratio of at least 70.
23. The process of claim 22 in which the zeolite beta seed are
substantially free of amorphous materials.
24. The process of claim 23 in which the zeolite beta seeds are
made from a reaction mixture which comprises one or more sources of
alkali metal cations, organic cation which is a tetraethylammonium
cation, an oxide of silicon, water and an oxide of aluminum and
having a reaction mixture in terms of mole ratios within the
following ranges:
where R is the organic cation and M is the alkali metal cation.
25. The process of claim 24 in which the reaction mixture for the
zeolite beta seeds includes triethanolamine, represented by X, in a
mole ratio of X/SiO.sub.2 ranging from about 0.2 to 0.8.
26. In a process for the production of zeolite beta by preparing a
reaction mixture which includes one or more sources of alkali metal
cations, tetraethylammonium cation, an oxide of silicon, water and
an oxide of aluminum wherein the improvement comprises preparing a
reaction mixture which includes one or more sources of alkali metal
cations, tetraethylammonium cation, an oxide of silicon, water, an
oxide of aluminum and triethanolamine, said reaction mixture having
mole ratios within the following ranges:
where R is the organic cation, M is the alkali metal cation and X
is the triethanolamine;
(b) maintaining the reaction mixture under conditions sufficient to
crystallize the zeolite Beta having a large crystal size which
ranges from 0.1 to 3.0 microns which is substantially free of
amorphous materials, said large crystal zeolite Beta having a
silica to alumina ratio of at least 20 to about 200; and
(c) recovering the zeolite Beta from step (b), the recovered
zeolite containing at least one organic cation and the
triethanolamine.
27. The process of claim 26 in which the organic cation represented
by R and the triethanolamine represented by X of the zeolite Beta
recovered in step (b) are converted at least in part into the
hydrogen form by calcining and exchange.
28. The process of claim 26 in which maintaining the reaction
mixture under conditions sufficient to crystallize the zeolite
includes temperatures ranging from 70.degree. C. to 175.degree.
C.
29. The process of claim 26 in which the organic cation source is
selected from the group consisting of tetraethylammonium hydroxide,
tetraethylammonium halide and a combination thereof.
30. The process of claim 29 in which the tetraethylammonium halide
source is selected from the group consisting of tetraethylammonium
bromide, tetraethylammonium chloride or tetraethylammonium
fluoride.
31. The process of claim 26 in which the zeolite beta has a
silica-to-alumina mole ratio of 20 to about 100.
32. The process of claim 1 in which the zeolite beta has a
silica-to-alumina mole ratio ranging from 20 to about 100.
33. In a process for the production of zeolite beta by preparing a
liquid synthesis mixture from which zeolite beta crystallizes which
includes one or more sources of alkali metal cations,
tetraethylammonium cation, an oxide of silicon, water and an oxide
of aluminum wherein the improvement comprises preparing a reaction
mixture which includes one or more sources of alkali metal cations,
tetraethylammonium cation, oxide of silicon, water, oxide of
aluminum and triethanolamine, said reaction mixture having mole
ratios within the following ranges:
where R is the tetraethylammonium cation, M is the alkali metal
cation and X is the triethanolamine;
(b) maintaining the reaction mixture under conditions sufficient to
crystallize the zeolite Beta which is substantially free of
amorphous materials, said zeolite Beta having a silica to alumina
ratio of at least 20 to about 1000; and
(c) recovering the zeolite Beta from step (b), the recovered
zeolite containing at least one organic cation and the
triethanolamine, said zeolite having a crystal size ranging from
0.1 to 3.0 microns.
34. The process of claim 33 in which the organic cation represented
by R and the triethanolamine represented by X of the zeolite Beta
recovered in step (b) are converted at least in part into the
hydrogen form by calcining and exchange.
35. The process of claim 33 in which maintaining the reaction
mixture under conditions sufficient to crystallize the zeolite
includes temperatures ranging from 70.degree. C. to 175.degree.
C.
36. The process of claim 33 in which the organic cation source is
selected from the group consisting of tetraethylammonium hydroxide,
tetraethylammonium halide and a combination thereof.
37. The process of claim 36 in which the tetraethylammonium halide
source is selected from the group consisting of tetraethylammonium
bromide, tetraethylammonium chloride or tetraethylammonium
fluoride.
38. The process of claim 33 in which the source of oxide of silicon
is colloidal silica.
39. The process of claim 33 in which the source of silica is
selected from the group consisting of precipitated silica and
silica precursor.
40. The process of claim 39 wherein the improvement further
comprises as a source of silica zeolite beta seeds having a
silica-to-alumina mole ratio of at least 70.
41. The process of claim 40 in which the zeolite beta seeds are
made by the process of claim 33.
42. A crystalline zeolite beta comprising the as-synthesized
composition identified in terms of mole ratios of oxides in the
anhydrous state: (3 to 60)R.sub.2 O:(0.5 to 12)M.sub.2/n O:Al.sub.2
O.sub.3 :(200 to 1000)SiO.sub.2 where M is an alkali metal cation
and R represents a tetraethylammonium cations and triethanolamine,
said zeolite beta having a crystal size ranging from 0.1 to 3.0
microns.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
Reference is made to U.S. patent application Ser. No. 07/715,190,
filed on Jun.14, 1991, entitled "Zeolite Beta". Cross Reference is
also made to U.S. patent application Ser. No. 07/715,189, filed on
Jun. 14, 1991. Both applications are incorporated herein by
reference
FIELD OF THE INVENTION
This invention relates to zeolite Beta, more specifically, a new
process for synthesizing zeolite Beta using triethanolamine in the
synthesis reaction mixture. The invention also relates to the use
of a precipitated silica and starter seeds as the silica source in
a reaction mixture which includes triethanolamine to achieve a
highly silicious zeolite Beta.
BACKGROUND OF THE INVENTION
Zeolitic materials, both natural and synthetic, have been
demonstrated to have catalytic properties for various types of
hydrocarbon conversion. Certain zeolitic materials are ordered,
porous crystalline aluminosilicates having a definite crystalline
structure as determined by X-ray diffraction, within which there
are a large number of smaller cavities which may be interconnected
by a number of still smaller channels or pores. These cavities and
pores are uniform in size within a specific zeolitic material.
These materials have become known as molecular sieves because the
dimensions of these pores can accept for adsorption molecules of
certain dimensions and reject those of larger dimensions. Such
molecular sieves, both natural and synthetic, include a wide
variety of positive ion-containing crystalline silicates. These
silicates can be described as rigid three-dimensional frameworks of
SiO.sub.4 and Periodic Table Group IIIA element oxide, e.g.,
AlO.sub.4, in which the tetrahedra are cross-linked by the sharing
of oxygen atoms whereby the ratio of the total Group IIIA element,
e.g., aluminum, and silicon atoms to oxygen atoms is 1:2. The
electrovalence of the tetrahedra containing the Group IIIA element,
e.g., aluminum, is balanced by the inclusion in the crystal of a
cation, e.g., an alkali metal or an alkaline earth metal cation.
This can be expressed wherein the ratio of the Group IIA element,
e.g., aluminum, to the number of various cations, such as Ca/2,
Sr/2, Na, K or Li, is equal to unity. One type of cation may be
exchanged either entirely or partially with another type of cation
utilizing conventional ion exchange techniques. By means of cation
exchange, it has been possible to vary the properties of a given
silicate by suitable selection of the cation. The spaces between
the tetrahedra are occupied by molecules of water prior to
dehydration.
Prior art techniques have resulted in the formation of a great
variety of synthetic zeolites. Many of these zeolites have come to
be designated by letter or other convenient symbols, as illustrated
by zeolite Z (U.S. Pat. No. 2,882,243); zeolite X (U.S. Pat. No.
2,882,244); zeolite Y (U.S. Pat. No. 3,130,007); zeolite ZK-5 (U.S.
Pat. No. 3,247,195); zeolite ZK-4 (U.S. Pat. No. 3,314,752);
zeolite ZSM-5 (U.S. Pat. No. 3,702,886); zeolite ZSM-11 (U.S. Pat.
No. 3,709,979); zeolite ZSM-12 (U.S. Pat. No. 3,832,449); zeolite
ZSM-20 (U.S. Pat. No. 3,972,983); zeolite ZSM-35 (U.S. Pat. No.
4,016,245); and zeolite ZSM-23 (U.S. Pat. No. 4,076,842), to name a
mere few.
The SiO.sub.2 /Al.sub.2 O.sub.3 of a given zeolite is often
variable. For example, zeolite X can be synthesized with SiO.sub.2
/Al.sub.2 O.sub.3 ratios of from 2 to 3; zeolite Y, from 3 to about
6. In some zeolites, the upper limit of the SiO.sub.2 Al.sub.2
O.sub.3 ratio is unbounded. ZSM-5 is one such example wherein the
SiO.sub.2 /Al.sub.2 O.sub.3 ratio is at least 5 and up to the
limits of present analytical measurement techniques. U.S. Pat. No.
3,941,871 (Re. 29,948) discloses a porous crystalline silicate made
from a reaction mixture containing no deliberately added alumina in
the recipe and exhibiting the X-ray diffraction pattern
characteristic of ZSM-5. U.S. Pat. Nos. 4,061,724, 4,073,865 and
4,104,294 describe crystalline silicates of varying alumina and
metal content.
It is generally known that the properties of zeolites can be
influenced by changing the structural silica-to-alumina mole
ratios. In synthesizing the zeolite the ratio can be varied by
altering the relative amounts of the silica and alumina-containing
precursor materials. For example increasing the silica relative to
the alumina usually results in a higher silica product. However, in
most zeolites after a certain silica-to-alumina mole ratio is
achieved, proportionally increasing the silica content of the
reactants does not necessarily increase the silica-to-alumina mole
ratio of the final product and can even hinder the formation of the
desired final product.
Zeolite Beta is a known zeolite which is described in U.S. Pat.
Nos. 3,308,069 and RE 28,341 both to Wadlinger, and reference is
made to these patents for a general description of zeolite Beta.
The zeolite Beta of Wadlinger is described as having a
silica-to-alumina ratio going from 10 to 100 and possibly as high
as 150.
Highly silicious zeolite Beta described as having silica-to-alumina
ratios within the range of 20-1000 is disclosed in Valyocsik et al,
U.S. Pat. No. 4,923,690. To achieve the high silica-to-alumina
ratio the zeolite is only partly crystallized. As the zeolite
becomes more fully crystalline, the silica-to-alumina ratio
decreases. This is demonstrated in the examples which show
achievement of highly silicious zeolite Beta at between 30 and 50%
crystallinity. It would be desirable to achieve a highly silicious
zeolite Beta which is fully crystalline.
The description of the zeolite Beta of the Wadlinger patents is
silent as to the crystallite size. Typically, however, the zeolite
Beta produced by the Wadlinger method is a small crystal zeolite
Beta having a crystal size ranging from 0.01 to 0.05 microns. For
certain applications, large crystal zeolites have been found to
possess distinct advantages over the smaller crystal zeolites.
Larger crystal zeolites are known to provide longer diffusion path
lengths which can be used to modify catalytic reactions. By way of
illustration only, in the medium pore zeolite ZSM-5, manipulating
crystal size in order to change the selectivity of the catalyst has
been described. A unique shape selective characteristic of ZSM-5 is
the para-selectivity in toluene disproportionation and aromatics
alkylation reactions. Increasing the size of the crystal, thereby
lengthening the diffusion path, is just one way of achieving a high
para-selectivity. The product selectivity occurs because an
increase in the diffusion constraints is imposed on the bulkier,
slower diffusing o- and m- isomers which reduces the production of
these isomers and increases the yield of the para-isomer. N.Y. Chen
et al, Shape Selective Catalysis in Industrial Applications, p.p.
51 (Marcel Dekker, Inc New York 1989) and N.Y. Chen et al,
Industrial Application of Shape Selective Catalysts, p.p. 196
(Catal. Rev. Sci. Eng. 28 (2&3) 1986). Obtaining high
selectivities in zeolite ZSM-5 by increasing the crystal size is
described in U.S. Pat. No. 4,517,402 which is incorporated herein
by reference. In U.S. Pat. No. 4,828,679 it is revealed that large
crystal ZSM-5 type zeolites have improved octane gain and total
motor fuel yield as well as improved steam stability. U.S. Pat. No.
4,650,656 describes a large crystal ZSM-5 which is synthesized by
controlling the reaction conditions such as the rate of addition of
the organics, the temperature, pH and the degree of agitation of
the crystallization media. The application of an external
gravitational force during the synthesis of silicalite has been
described as a means for producing a large crystal zeolite in D. T.
Hayhurst et al, "Effect of Gravity on Silicalite Crystallization"
in Zeolite Synthesis p.p. 233 (M. L. Occelli Ed. American Chemical
Society 1956). In J. F. Charnell, "Gel Growth of Large Crystals of
Sodium A and Sodium X Zeolites", Jour. Crystal Growth 8, pp.
291-294, (North Holland Publishing Co., 1971), a method of
synthesizing large crystal zeolite A and zeolite X is described in
which, as the only organic reactant, triethanolamine is
incorporated into the reaction mixture. A review of these
publications reveals that a significant amount of attention has
been directed to synthesizing large crystal zeolites yet none of
the publications point to a consistent method for producing the
large crystals. The crystal size of zeolite Beta was generally
related to the silica-to-alumina ratio, the highly silicious
zeolite Beta corresponding to a larger crystal size and the lower
silica-to-alumina mole ratio zeolite Beta corresponding to a
smaller crystal size. Techniques for synthesizing a large crystal
zeolite Beta covering a broad range of silica-to-alumina ratios,
including the high as well as the low silica-to-alumina ratios,
would be desirable.
SUMMARY OF THE INVENTION
A method for synthesizing zeolite Beta which has catalytic activity
is described herein. The zeolite Beta is highly crystalline and is
synthesized over a broad range of silica-to-alumina ratios in the
as-synthesized form using triethanolamine along with a colloidal
silica or a precipitated silica and seeds in the synthesis
mixture.
It is an object of the invention to produce a highly crystalline
zeolite Beta having a broad range of silica to alumina ratios.
It is a further object of the invention to produce a large crystal
zeolite Beta.
It is a feature of the invention to synthesize zeolite Beta from a
synthesis mixture containing triethanolamine in addition to a
source of silica, caustic and an organic directing agent and,
optionally, alumina to provide a large crystal zeolite Beta which
is fully crystalline and covers a broad range of silica to alumina
ratios.
It is another feature of the invention to synthesize zeolite Beta
with triethanolamine in the synthesis mixture along with a
precipitated silica and starter seeds as the silica source to
produce a fully crystalline highly silicious zeolite Beta.
It is still a further feature of the invention to synthesize
zeolite Beta from silica sources having a high solids content.
In preparing as-synthesized highly silicious zeolites, silica is
the major component of the reaction mixture. High silica levels in
formulations of highly silicious zeolites, utilizing conventional
procedures, become highly viscous as the silica increases and
impede agitation of the synthesis mixture. An advantage of the
instant invention is that it provides a highly crystalline highly
silicious zeolite Beta which is synthesized without the problems
associated with conventional high silica formulations.
DETAILED DESCRIPTION OF THE INVENTION
The method of synthesizing a highly crystalline zeolite Beta having
a broad range of silica-to-alumina ratios comprises forming a
synthesis mixture containing one or more sources of alkali metal
cations, organic nitrogen-containing cations, oxides of aluminum,
oxides of silicon, triethanolamine and water and has a composition,
in terms of mole ratios within the ranges recited in the following
Table A:
TABLE A ______________________________________ Broad Preferred
______________________________________ SiO.sub.2 /Al.sub.2 O.sub.3
= 20->1000 70-1000 OH.sup.- /SiO.sub.2 = 0.1-0.8 0.2-0.4
R/SiO.sub.2 = 0.3-1.0 0.3-0.9 H.sub.2 O/SiO.sub.2 = 5-40 5-15
M/SiO.sub.2 = 0.01-0.2 0.01-0.07 X/SiO.sub.2 = 0.1-1.0 0.2-0.8
R.sub.1 /R.sub.1 + R.sub.2 = 0.1-1.0 0.2-0.8
______________________________________ R = organic
nitrogencontaining cations; R.sub.1 = tetraethylammonium hydroxide;
R.sub.2 = tetraethylammonium halide; M = alkali metal cation; and X
= triethanolamine.
The mixture is maintained under conditions sufficient to
crystallize the silicate.
The zeolite Beta is highly crystalline which means that the zeolite
Beta is substantially free of amorphous silica and alumina unlike
the partially crystalline zeolite Beta described in U.S. Pat. No.
4,923,690. In order to achieve high crystallinity the synthesis
should be carried out until the product is at least about 70%
crystalline, ranging from 80% to 130% crystalline, preferably at
least about 90% crystalline as determined by traditional X-ray
analysis techniques.
The reaction mixture for the synthesis of fully crystalline zeolite
Beta can be prepared utilizing materials which supply the
appropriate oxide. Such compositions include aluminates, alumina,
precipitated silica, silica hydrosol, silica precursor, silica gel,
silicic acid and hydroxides.
Each oxide component utilized in the reaction mixture for preparing
the zeolite can be supplied by one or more essential reactants and
they can be mixed together in any order. For example, any oxide can
be supplied by an aqueous solution, sodium hydroxide or by an
aqueous solution of a suitable silicate; the organic cation can be
supplied by the directing agent compound of that cation, such as,
for example, the hydroxide or salt, e.g. halide, such as chloride,
iodide, fluoride or bromide. The reaction mixture can be prepared
either batchwise or continuously.
The zeolite Beta can also be synthesized in the absence of other
sources of zeolite framework elements such as aluminum. Thus, the
zeolite synthesis mixture will be substantially free of added
alumina or alumina source. However alumina may be present in the
synthesis mixture as an impurity in the starting materials. As an
impurity, alumina may be present in amounts of less than 0.5 wt.%,
preferably, less than 0.2 wt.%.
The organic reactants include at least one organic directing agent
which is an organic nitrogen-containing cation and
triethanolamine.
The directing agent for the present method is at least one
tetraethylammonium compound or mixtures thereof: non-limiting
examples of the directing agent include the hydroxide and/or the
halide, e.g., tetraethylammonium hydroxide (TEAOH),
tetraethylammonium bromide (TEABr), tetraethylammonium chloride
(TEACl) and tetraethylammonium fluoride (TEAF). The triethanolamine
is a tertiary alkanolamine.
The triethanolamine allows a high silica content starting material
such as a precipitated silica to be used in synthesizing the highly
silicious zeolite Beta. The triethanolamine helps to fluidize the
high silica-content mixture which facilitates stirring or agitating
the mixture during formation of the zeolite. The triethanolamine
also allows less water to be used in the synthesis mixture, i.e.
H.sub.2 O/SiO.sub.2 ranging from 5 to 10, which favors formation of
the pure, fully crystalline material. Excess water is undesirable
because it results in the formation of an impure product which
contains materials other than zeolite Beta, such as ZSM-12.
Although extra tetraethylammonium hydroxide can be used to supply
adequate fluidity, it is not an economical alternative and does not
dependably produce fully crystalline large crystals.
Triethanolamine is available commercially and is described in
Hawley's Condensed Chemical Dictionary, pp. 1179-1180, N. I. Sax et
al., 11th ed. (Van Nostrand Reinhold Co., N.Y., 1987) which is
incorporated herein by reference as to that description.
The zeolite Beta composition as prepared hereby can be identified,
in terms of mole ratios of oxides and in the as synthesized
anhydrous state, as follows:
(3 to 60)R.sub.2 O:(0.5 to 12)M.sub.2/n O:Al.sub.2 O.sub.3 :(20 to
>1000)SiO.sub.2 where M is the alkali metal cation and R
represents the organic cations. The term organic cation as used
here includes the organic directing agent and the
triethanolamine.
The zeolite Beta described herein is considered a large crystal
having been synthesized in crystal sizes from at least 0.1 to 0.2
microns ranging from 0.2 to 3.0 microns, more specifically from 0.2
to 2.0 microns. This is a significant advance in magnitude over the
small crystal zeolite Beta which ranges in crystal size from 0.01
to 0.05 microns.
The determination of crystal size, is described in more complete
detail in U.S. Pat. No. 4,828,679 which is incorporated herein by
reference. Basically, crystal size is determined by conventional
scanning electron microscopy (SEM) or transmission electron
microscopy (TEM). The minimum crystal size of a given crystal is
taken as the dimension of a reference. The amount of large crystal
zeolite Beta synthesized in accordance with this invention can be
present in predominant proportions; i.e., exceeding 50 wt. % and
preferably may constitute up to 100 wt.% of the total zeolite
synthesized.
In the method of forming the highly silicious zeolite material,
which is defined as such by having a silica-to-alumina ratio over
100, preferably in a range of 200 to >1000, an amorphous
precipitated silica or silica precursor can be the silica source.
The precipitated silica precursors contain clustered solids which
exhibit low viscosities even at high solids content in the
synthesis mixture and have a solids (silica) content of at least
about 10 wt.%, preferably from 30 to 90 wt.%. Precipitated silica
is formed from the vapor phase or by precipitation from solution
such as sodium silicate solution. The process is described in more
complete detail in Kirk-Othmer's "Encyclopedia of Chemical
Technology" 3rd Ed., Vol. 20, p.p. 776 (John Wiley & Sons,
1982) which is incorporated herein by reference. The precipitated
silica may range in particle size from 0.01 to 100 microns,
preferably having a size of about 0.02 microns. The advantage of
using a precipitated silica is that the reaction mixture has a
higher solids content, greater than about 10 wt.% by weight which
effects a cost reduction. Representative examples of commercially
available precipitated silicas include the solid silica, Ultrasil
(a precipitated, spray dried silica containing about 90 wt.%
silica) and HiSil (a precipitated hydrated silica containing about
87 wt.% silica) and RTM.
A silica source which can also be used as the source for silica is
an amorphous silica precipitate made from a solution of soluble
silica source which is called a silica precursor. The silica
precursor is described in U.S. Pat. No. 4,983,275, and the
description of the silica source is incorporated herein by
reference.
In preparing the highly silicious zeolites using a precipitated
silica, special starter seeds are included in the reaction mixture.
The special seeds are preferably highly silicious e.g., having a
silica-to-alumina mole ratio of at least 70 and high purity zeolite
Beta. Low silica seeds are undesirable as they tend to promote the
formation of a product containing impurities such as ZSM-12 or
ZSM-15. The reaction mixture for the special seeds comprises
sources of alkali metal cations, oxides of aluminum, oxides of
silicon and at least one organic directing agent and water. The
special starter seeds may or may not contain added alumina. Thus,
in the high silica seed reaction mixture, any alumina contained in
the synthesis mixture exists as an impurity. The mixture can,
optionally contain triethanolamine. The final zeolite Beta product
can also be "self-seeding" which means that the reaction synthesis
for the starter seeds is almost identical to the reaction synthesis
for the final product.
The silica-to-alumina ratios referred to herein are the framework
ratios. Thus, as known in the art, the ratio of the SiO.sub.4 to
the AlO.sub.4 tetrahedra make up the structure of the zeolite Beta.
The ratio may vary from the ratio determined by various known
physical and chemical methods which are described more completely
in U.S. Pat. No. 4,419,220 which is incorporated herein by
reference.
Crystallization of the material can be carried out at either static
or stirred conditions. The agitation can vary from 0 to 400 rpms,
in a suitable reactor vessel. Suitable vessels include
polypropylene, teflon coated or stainless steel autoclaves. The
range of temperatures necessary to fully crystallize the zeolite
Beta range from about 70.degree. C. to 175.degree. C., preferably
about 140.degree. C. The amount of time required for
crystallization ranges from about at least 16 hours to 90 days.
Thereafter, the crystals are recovered.
The hydrogen form of the as-synthesized zeolite can be prepared by
calcining in air in an inert atmosphere at a temperature ranging
from 200.degree. C. to 900.degree. C. or higher and exchange of the
alkali metal cation.
The hydrogen form of the highly silicious zeolite was found to have
a low alpha value, a low value being characterized as at least
about 1, ranging from 1 to 50. When alpha value is examined, it is
noted that the alpha value is an approximate indication of the
catalytic cracking activity of the catalyst compared to a standard
catalyst and it gives the relative rate constant (rate of normal
hexane conversion per volume of catalyst per unit time). It is
based on the activity of silica-alumina cracking catalyst taken as
an Alpha of 1 (Rate Constant=0.016 sec.sup.-1). The alpha test is
described in U.S. Pat. No. 3,354,078; in the Journal of Catalysis,
Vol. 4, p. 527 (1965); Vol. 6, p. 278 (1966); and Vol. 61, p. 395
(1980), each incorporated herein by reference as to that
description. The experimental conditions of the test used herein
include a constant temperature of 538.degree. C. and a variable
flow rate as described in detail in the Journal of Catalysis Vol.
61, p. 395. The higher alpha values correspond with a more active
catalyst.
The original cation can be replaced, at least in part, by
calcination and/or ion exchange with another cation. Thus, the
original cations are exchanged into a hydrogen or hydrogen ion
precursor form or a form in which the original cation has been
replaced by a metal of Groups IIA, IIIA, IVA, IIIB, IVB, VIB or
VIII of the Periodic Table of the Elements. Thus, for example, the
original cations can be exchanged with ammonium cations or
hydronium ions. Catalytically active forms of these would include,
in particular, hydrogen, rare earth metals, aluminum metals of
Groups II and VII of the Periodic Table and manganese. The original
cation can be replaced by methods which include ion exchange,
impregnation or by physical admixture.
The X-ray diffraction patterns of the crystalline silicate
identified as zeolite Beta are shown in U.S. Pat. No. 3,308,069,
herein incorporated by reference, in its entirety. The known
methods of structural determination used to evaluate the instant
zeolite Beta will be found there as well. The X-ray diffraction
pattern of crystalline silicate having the structure of zeolite
Beta made in accordance with the instant invention has the
characteristic lines which fall within the ranges of the general
zeolite Beta pattern.
Steaming, a known technique, can be used to increase the
silica-to-alumina ratio. Steaming is conducted with 0.01 to 1.0
atm. of water in air at a temperature of at least 600.degree. F.,
preferably at least about 650.degree. F. for about 1 to 48 hours,
preferably 3 to 24 hours. To increase the silica-to-alumina ratio
further the catalyst can be subjected to acid treatment with a
mineral acid alone or along with the steam treatment. Such methods
are described, in further detail in U.S. Pat. No. 4,740,292 which
is incorporated herein by reference, in its entirety. It is often
desirable to incorporate the zeolites into a material resistant to
the temperature and other conditions employed in the process. Such
matrix materials include synthetic and naturally occurring
substances, such as inorganic materials, e.g., clay, silica and
metal oxides. The latter may be either naturally occurring or in
the form of gelatinous precipitates or gels, including mixtures of
silica and metal oxides. Naturally occurring clays can be
composited with the zeolites, including those of the
montmorillonite and kaolin families. These clays can be used in the
raw state as originally mined or initially subjected to
calcination, acid treatment or chemical modification to enhance
their activity. The relative proportions of zeolite component and
inorganic oxide gel matrix on an anhydrous basis may vary widely
with the zeolite content ranging from 5 to 80, more usually 10 to
70 wt % of the dry composite. The matrix itself may possess
catalytic properties, generally of an acidic nature.
In addition to the foregoing materials, the zeolite Beta catalyst
can be composited with a porous matrix material such as
silica-alumina, silica-magnesia, silica-zirconia, silica-thoria,
silica-beryllia, silica-titania as well as ternary compositions
such as silica-alumina-thoria, silica-alumina-zirconia,
silica-alumina-magnesia and silica-magnesia-zirconia. The matrix
can be in the form of a cogel. A mixture of these components can
also be used. The relative proportions of the crystalline silicate
and inorganic oxide gel matrix may vary widely with the crystalline
silicate content ranging from about 1 to 90 percent by weight,
usually from about 2 to about 50 percent by weight of the
composite.
CATALYST APPLICATION
While the crystalline silicate of the present invention may be used
in a wide variety of organic compound conversion reactions, it is
notably useful in cracking, hydrocracking, lubricant dewaxing, wax
isomerization, olefin isomerization, oxygenate formation, olefin
polymerization (oligomerization).
In catalytic dewaxing, the base-exchanged highly silicious zeolite
Beta will be most suitable. A catalytic dewaxing process using
zeolite Beta is described in U.S. Pat. No. 4,419,220 to LaPierre et
al, the entire contents of which are incorporated by reference. The
process is preferably carried out in the presence of hydrogen at
temperatures ranging from about 250.degree. C. to 500.degree. C.
under conditions of pressure ranging from atomospheric to 25,000
kPa (3,600 psig), the higher pressures being preferred. The
n-paraffins of the feed are isomerized to form branched chain
products.
In catalytic cracking, the zeolite Beta can be used as a stand
alone or an additive catalyst along with another molecular sieve
cracking component, typically a faujasite, representative examples
of which include a Y-type zeolite such as REY, USY, RE-USY,
dealuminated Y and silicon-enriched Y. The molecular sieve catalyst
can also be ZSM-5. A more complete description of the use of
zeolite Beta in cracking reactions can be found in U.S. Pat. No.
4,740,292.
The following examples describe the invention in more complete
detail.
EXAMPLE 1
Colloidal silica (30% solids), 101.4 parts is added to a solution
containing 1.0 part sodium aluminate (43.3% Al.sub.2 O.sub.3, 32.2
% Na.sub.2 O), 55.8 parts of 40% tetraethylammonium hydroxide
solution (TEAOH), 64.8 parts of 50% tetraethylammonium bromide
solution (TEABr) and 31.5 parts tetraethylammonium bromide solid.
To this is added 17.0 parts of triethanolamine (TEA).
The composition of the reaction mix is as follows, in mole
ratios:
______________________________________ SiO.sub.2 /Al.sub.2 O.sub.3
= 119 OH.sup.- /SiO.sub.2 = 0.32 R.sub.1 + R.sub.2 /SiO.sub.2 =
0.90 H.sub.2 O/SiO.sub.2 = 15.0 Na.sup.+ /SiO.sub.2 = 0.02
TEA/SiO.sub.2 = 0.22 R.sub.1 /R.sub.1 0.33.sub.2 =
______________________________________
where R.sub.1 =TEAOH and R.sub.2 =TEABr.
The mixture is crystallized in a static reactor at 143.degree. C.
for 8 days. The solid product is filtered, water washed and dried
at 120.degree. C.
The X-ray analysis of the product is zeolite Beta, 115%
crystallinity. Scanning electron micrographs of the material show
crystals of 0.5-0.75 micron size. The chemical composition of the
product is, in wt.%:
______________________________________ C 9.69 N 1.71 Na 0.45
Al.sub.2 O.sub.3 1.1 SiO.sub.2 75.6 Ash 77.7 SiO.sub.2 /Al.sub.2
O.sub.3 117 ______________________________________
The sorption capacities, after calcining for 3 hours at 538.degree.
C. are, in wt.%.
______________________________________ Cyclohexane, 40 Torr 21.2
n-Hexane, 40 Torr 17.9 H.sub.2 O, 12 Torr 20.6 Surface area,
m.sup.2 /g 600 ______________________________________
The produce of this Example is determined to have the X-ray
diffraction pattern shown below:
TABLE 2 ______________________________________ X-ray Diffraction
Pattern of Zeolite Beta 2-Theta d(Angstroms) I/I.sub.o
______________________________________ 7.58 11.65 11 11.66 7.58 2
16.64 5.32 5 17.88 4.96 2 18.34 4.83 2 21.58 4.11 16 22.61 3.93 100
25.46 3.50 7 26.85 3.32 16 29.04 3.07 3 29.61 3.01 14 30.68 2.91 4
33.57 2.67 4 34.68 2.58 2 43.90 2.07 11 44.63 2.03 2 49.90 1.83 2
52.66 1.74 2 55.22 1.66 3
______________________________________
EXAMPLE 2
Colloidal silica (30%), 84.2 parts, is added to a solution
containing 1.0 part sodium aluminate (43.3% Al.sub.2 O.sub.3, 32.2%
Na.sub.2 O), 73.7 parts H.sub.2 O, 6.8 parts tetraethylammonium
fluoride (TEAF), 33.2 parts of 40% tetraethylammonium hydroxide
solution (TEAOH) and 10.5 parts triethanolamine (TEA).
The composition of the reaction mixture in mole ratios is as
follows:
______________________________________ SiO.sub.2 /Al.sub.2 O.sub.3
= 99 OH.sup.- /SiO.sub.2 = 0.44 R.sub.1 + R.sub.2 /SiO.sub.2 = 0.32
H.sub.2 O/SiO.sub.2 = 20.6 Na.sup.+ /SiO.sub.2 = 0.22 R.sub.1
/R.sub.1 + R.sub.2 = 0.66 TEA/SiO.sub.2 = 0.17
______________________________________
where R.sub.1 =TEAOH and R.sub.2 =TEAF
The mixture is crystallized in a static reactor at 130.degree. C.
for 21 days. The solid product is filtered, water washed and dried
at 120.degree. C. Scanning electron micrographs of the material
reveal crystals of 0.3-1.0 micron in size. The X-ray analysis of
the product shows it to be zeolite Beta, 110% crystalline, with the
characteristic lines shown in Table 3:
TABLE 3 ______________________________________ Interplanar
d-Spacing (A) Relative Intensity (I/I.sub.o)
______________________________________ 11.5 .+-. 0.3 M-S 7.4 .+-.
0.2 W 6.6 .+-. 0.15 W 4.15 .+-. 0.1 W 3.97 .+-. 0.1 .sup. VS 3.00
.+-. 0.07 W 2.05 .+-. 0.05 W
______________________________________
The chemical composition of the product is in wt.%:
______________________________________ N = 1.62 Na = 0.29 Al.sub.2
O.sub.3 = 2.8 SiO.sub.2 = 74.5 Ash = 79.7 SiO.sub.2 /Al.sub.2
O.sub.3 = 45.2 ______________________________________
EXAMPLE 3
Colloidal silica (30% SiO.sub.2), 101.4 parts, is added to a
solution containing sodium aluminate (1 part), 55.8 parts of
tetraethylammonium hydroxide (TEAOH) solution, 64.8 parts of 50%
tetraethylammonium bromide (TEABr) solution, 31.5 parts solid TEABr
and 17.0 parts triethanolamine (TEA).
The composition of the reaction mixture in mole ratios is as
follows:
______________________________________ SiO.sub.2 /Al.sub.2 O.sub.3
= 119 OH.sup.- /SiO.sub.2 = 0.32 R.sub.1 + R.sub.2 /SiO.sub.2 =
0.90 R.sub.1 /R.sub.1 + R.sub.2 = 0.33 H.sub.2 O/SiO.sub.2 = 15.0
Na.sup.+ /SiO.sub.2 = 0.02 TEA/SiO.sub.2 =2 0.22
______________________________________
where R.sub.1 =TEAOH and R.sub.2 =TEABr
The mixture is crystallized in a static reactor at 140.degree. C.
for 8 days.
The X-ray analysis of the washed, dried (120.degree. C.) material
was zeolite Beta, 125% crystalline. The material has the
characteristic X-ray diffraction shown in Table 2. Scanning
electron micrographs show crystals of 0.3-0.5 microns.
The chemical composition of the product was, in wt.%:
______________________________________ N = 1.70 Na = 0.53 Al.sub.2
O.sub.3 = 1.2 SiO.sub.2 = 75.2 Ash = 78.1 SiO.sub.2 /Al.sub.2
O.sub.3 = 106 ______________________________________
The sorption capacities, after calcining for 16 hours at
538.degree. C. are, in wt.%:
______________________________________ Cyclohexane, 40 Torr 20.6
n-Hexane, 40 Torr 18.1 H.sub.2 O, 12 Torr 15.5 Surface area,
m.sub.2 /g 617 ______________________________________
The following examples demonstrate the synthesis of highly
silicious zeolite Beta synthesis in which the silica sources are
precipitated silica and starter seeds.
EXAMPLE 4
Ultrasil, a precipitated silica, 11.5 parts is added to a solution
containing 1 part 50% NaOH solution, 40% tetraethylammonium
hydroxide (TEAOH) solution, 20.3 parts, triethanolamine (TEA), 17.3
parts, and H.sub.2 O, 4.92 parts. To this mixture is added 1.18
parts of zeolite Beta seeds (78% solids, 110/1 SiO.sub.2 /Al.sub.2
O.sub.3). The mixture has the following composition in mole
ratios:
______________________________________ OH.sup.- /SiO.sub.2 = 0.39
R/SiO.sub.2 = 0.32 H.sub.2 O/SiO.sub.2 = 5.65 Na.sup.+ /SiO.sub.2 =
0.07 TEA/SiO.sub.2 = 0.67
______________________________________
Where R=TEAOH
Any alumina present exists as an impurity in the silica source.
The mixture is crystallized, with stirring, 300 rpm, for 16 hours
at room temperature, followed by 10 days at 135.degree. C. The
X-ray analysis shows the product to be zeolite Beta, 95%
crystalline, with a trace of unidentified crystalline material. The
scanning electron micrographs shows the material to be 0.3-0.8
microns in size.
The chemical composition of the product is, in wt.%:
______________________________________ N 1.61 Na 1.1 Al.sub.2
O.sub.3 0.20 SiO.sub.2 75.5 Ash 78.4 SiO.sub.2 /Al.sub.2 O.sub.3
642 ______________________________________
The sorption capacities, after calcining for 3 hours at 538.degree.
C. are, in wt.%:
______________________________________ Cyclohexane, 40 Torr. 13.5
n-Hexane, 40 Torr. 10.8 H.sub.2 O, 12 Torr. 4.9 Surface area,
m.sub.2 /g 333 ______________________________________
EXAMPLE 5
This example demonstrates the preparation of the high silica, high
purity seeds used in several of the examples. 33.8 Parts of
Ultrasil 90% solids, precipitated silica, were added to a solution
containing 1 part of sodium aluminate (43.3% Al.sub.2 O.sub.3,
32.2% Na.sub.2 O), 55.8 parts of 40% tetraethylammonium hydroxide
solution (TEAOH) and 127.9 parts of 50% tetraethylammonium bromide
(TEABr) solution. The composition of the reaction mixture in mole
ratios:
______________________________________ SiO.sub.2 /Al.sub.2 O.sub.3
= 119 OH.sup.- /SiO.sub.2 = 0.32 R.sub.1 + R.sub.2 /SiO.sub.2 =
0.90 H.sub.2 O/SiO.sub.2 = 10.7 Na.sup.+ /SiO.sub.2 = 0.02 R.sub.1
/R.sub.1 + R.sub.2 = 0.33
______________________________________
where R.sub.1 =TEAOH, R.sub.2 =TEABr
The mixture was crystallized at 138.degree. C., 45 rpm, for 51
hours. At that time, x-ray analysis showed it was beta zeolite,
110% crystalline.
The chemical composition of the product was, in wt. %:
______________________________________ N 2.01 Na 0.59 Al.sub.2
O.sub.3 0.98 SiO.sub.2 74.3 Ash 76.9 SiO.sub.2 /Al.sub.2 O.sub.3
129 ______________________________________
The sorption capacities, after calcining for three hours at
538.degree. C. are, in wt. %:
______________________________________ Cyclohexane, 40 Torr 22.1
H.sub.2 O, 12 Torr 15.0 Surface Area, m.sup.2 /g 681
______________________________________
EXAMPLE 6
Ultrasil, 90% solids 11.5 parts, was added to a solution containing
one part of 50% NaOH solution, 20.3 parts of 40% TEAOH solution,
17.3 parts of triethanolamine (TEA) and 4.92 parts of H.sub.2 O. To
this slurry, was added 1.13 parts of the seeds from example 5. The
mixture had the following composition in mole ratios:
______________________________________ OH.sup.- /SiO.sub.2 = 0.39
R/SiO.sub.2 = 0.32 H.sub.2 O/SiO.sub.2 = 5.6 Na.sup.+ /SiO.sub.2 =
0.07 TEA/Si = 0.67 ______________________________________
The mixture was crystallized at 45 rpm, for 16 hours at room
temperature, followed by 23 hours at 138.degree. C. The x-ray
analysis of the washed, dried (120.degree. C.) product was beta
zeolite, 105% crystalline.
The chemical composition of the product was, in wt. %:
______________________________________ N 1.91 Na 0.36 Al.sub.2
O.sub.3, ppm 1580 SiO.sub.2 72.3 SiO.sub.2 /Al.sub.2 O.sub.3 778
______________________________________
The sorption capacities, after calcining for three hours at
538.degree. C. are, in wt. %:
______________________________________ Cyclohexane, 40 Torr 20.0
H.sub.2 O, 12 Torr 7.2 Surface Area, m.sup.2 /g 501
______________________________________
A portion of the product of this example was calcined in air for
three hours at 538.degree. C., ammonium exchanged and converted to
the hydrogen form. It had an alpha value of 12.
EXAMPLE 7
The same reactants as in Example 6 were used, except that 0.75
parts of Example 5 seeds were used. The mixture was crystallized at
45 rpm for 16 hours at room temperature, followed for 28 hours at
138.degree. C. The x-ray analysis of the washed product showed
zeolite beta, 100% crystalline.
The chemical composition of the product was, in wt. %:
______________________________________ N 1.85 Na 0.78 Al.sub.2
O.sub.3 0.27 SiO.sub.2 73.8 Ash 77.1 SiO.sub.2 /Al.sub.2 O.sub.3
465 ______________________________________
The sorption capacities, after calcining for three hours at
538.degree. C. are, in wt. %:
______________________________________ Cyclohexane, 40 Torr 21.7
H.sub.2 O, 12 Torr 16.0 ______________________________________
A portion of the material obtained in this example was calcined in
air, ammonium exchanged and converted to the hydrogen form. The
alpha value of this example was 7.
EXAMPLE 8
The procedure of example 6 was repeated, except that 0.56 parts of
Example 5 seeds were used. The mixture was crystallized for 16
hours at room temperature followed by 40 hours at 138.degree. C.
The washed product was identified as beta zeolite, 100%
crystalline. The chemical composition of the product was, in wt.
%:
______________________________________ N 1.86 Na 0.82 Al.sub.2
O.sub.3 0.23 SiO.sub.2 71.3 Ash 72.5 SiO.sub.2 /Al.sub.2 O.sub.3
527 ______________________________________
The sorption capacities, after calcining for three hours at
538.degree. C. are, in wt. %:
______________________________________ Cyclohexane, 40 Torr 18.9
H.sub.2 O, 12 Torr 14.6 Surface Area, m.sup.2 /g 527
______________________________________
The hydrogen form material of this example had an alpha value of
two.
EXAMPLE 9
This example demonstrates self-seeding. The same reactants shown in
example 6 were used, except that 0.56 parts of zeolite Beta seeds
synthesized in example 6 were used to seed the reaction. The
mixture was crystallized at 45 rpm for 16 hours at room
temperature, followed by 143 hours at 138.degree. C. The washed
product was beta zeolite, 80% crystalline.
The chemical composition of the product was, in wt. %:
______________________________________ N 2.0 Na 1.6 Al.sub.2
O.sub.3, ppm 1390 SiO.sub.2 77.7 SiO.sub.2 /Al.sub.2 O.sub.3 950
______________________________________
EXAMPLE 10
This is a comparative example which shows the importance of using
high purity, high silica to alumina seeds.
The same reactants of example 6 were used. The seeds used were 1.13
parts of beta zeolite, 65% crystalline, 38/1 silica to alumina. The
mixture was crystallized 16 hours at room temperature, followed by
10 days at 138.degree. C. The product was analyzed as a mixture of
beta zeolite and ZSM-12.
EXAMPLE 11
This example demonstrates that a mixture of TEABr and TEAOH can be
used in the synthesis. This would reduce production cost.
One part of 50% NaOH solution is added to a solution containing
15.2 parts of 40% TEAOH solution and 5.8 parts of 50% TEABr
solution and 4.9 parts of H20. 17.4 parts of TEA are added,
followed by 11.6 parts of precipitated silica and 1.2 parts of beta
seeds (118/1 SiO.sub.2 /Al.sub.2 O.sub.3). The composition of the
reaction mixture in mole ratios:
______________________________________ OH.sup.- /SiO.sub.2 = 0.31
R.sub.1 + R.sub.2 /SiO.sub.2 = 0.32 H.sub.2 O/SiO.sub.2 = 5.6
Na.sup.+ /SiO.sub.2 = 0.07 TEA/SiO.sub.2 = 0.67 R.sub.1 /R.sub.1 +
R.sub.2 = 0.75 ______________________________________
The mixture was crystallized with stirring for 16 hours at room
temperature followed by 10 days at 132.degree. C. The product was
analyzed as 100% beta zeolite.
The chemical composition of the product was, in wt. %:
______________________________________ N 1.65 Na 0.97 Al.sub.2
O.sub.3 0.22 SiO.sub.2 74.4 SiO.sub.2 /Al.sub.2 O.sub.3 575
______________________________________
The sorption capacities, after calcining for three hours at
538.degree. C. are, in wt. %:
______________________________________ Cyclohexane, 40 Torr 21.1
H.sub.2 O, 12 Torr 6.9 Surface area, m.sup.2 /g 645
______________________________________
* * * * *